Compositions and methods for thermosetting molecules in organic compositions

ABSTRACT

In a method of producing a low dielectric constant polymer, a thermosetting monomer is provided, wherein the thermosetting monomer has a cage compound or aryl core structure, and a plurality of arms that are covalently bound to the cage compound or core structure. In a subsequent step, the thermosetting monomer is incorporated into a polymer to form the low dielectric constant polymer, wherein the incorporation into the polymer comprises a chemical reaction of a triple bond that is located in at least one of the arms. Contemplated cage compounds and core structures include adamantane, diamantane, silicon, a phenyl group and a sexiphenylene group, while preferred arms include an arlyene, a branched arylene, and an arylene ether. The thermosetting monomers may advantageously be employed to produce low-k dielectric material in electronic devices, and the dielectric constant of the polymer can be controlled by varying the overall length of the arms.

This application is a divisional of allowed application Ser. No.09/618,945, filed Jul. 19, 2000 now U.S. Pat. No. 6,469,123.

FIELD OF THE INVENTION

The field of the invention is reduction of dielectric constants.

BACKGROUND OF THE INVENTION

As interconnectivity in integrated circuits increases and the size offunctional elements decreases, the dielectric constant of insulatormaterials embedding the metallic conductor lines in integrated circuitsbecomes an increasingly important factor influencing the performance ofthe integrated circuit. Insulator materials having low dielectricconstants (i.e., below 3.0) are especially desirable, because theytypically allow faster signal propagation, reduce capacitive effects andcross talk between conductor lines, and lower voltages to driveintegrated circuits.

Since air has a dielectric constant of about 1.0, a major goal is toreduce the dielectric constant of insulator materials down towards atheoretical limit of 1, and several methods are known in the art forincluding air into the insulator materials to reduce the dielectricconstant of such materials. In some methods, air is introduced into theinsulator material by generating nanosized voids in a compositioncomprising an adequately crosslinked thermostable matrix and athermolabile (thermally decomposable) portion, which is eitherseparately added to the thermostable matrix material (physical blendingapproach), or built-in into the matrix material (chemical graftingapproach). In general, the matrix material is first crosslinked at afirst temperature to obtain a three-dimensional matrix, then thetemperature is raised to a second, higher temperature to thermolyze thethermolabile portion, and cured at a third, still higher temperature toanneal and stabilize the desired nanoporous material that has voidscorresponding in size and position to the size and position of thethermolabile portion.

In both the physical blending approach and the chemical graftingapproach, nanoporous materials with desirable dielectric constants ofabout 2.5 and below may be achieved. However, while there is typicallyonly poor control over pore size and pore distribution in the physicalblending approach, the chemical grating approach frequently posessignificant challenges in the synthesis of the polymers and prepolymersand inclusion of various reactive groups (e.g., to enable crosslinking,addition of thermolabile groups, etc.) into the polymers andprepolymers. Moreover, the chemical nature of both the thermolabileportion and thermostable matrix generally limits processing temperaturesto relatively narrow windows which must distinguish the crosslinking(cure) temperature, thermolysis temperature and glass transitiontemperature, thereby significantly limiting the choice of availablematerials.

In other methods, air or other gas (i.e. voids) is introduced into theinsulator material by incorporation of hollow, nanosized spheres in thematrix material, whereby the nanosized spheres acts as a “voidcarriers”, which may or may not be removed from the matrix material. Forexample, in U.S. Pat. No. 5,458,709 to Kamezaki et al., the inventorsteach the use of hollow glass spheres in an insulator material. However,the distribution of the glass spheres is typically difficult to control,and with increasing concentration of the glass spheres, the dielectricmaterial loses flexibility and other desirable physico-chemicalproperties. Furthermore, glass spheres are generally larger than 20 nm,and are therefore not suitable for nanoporous materials where poressmaller than 2 nm are desired.

To produce pores with a size substantially smaller than glass spheres,Rostoker et al. describe in U.S. Pat. No. 5,744,399 the use offullerenes as void carriers. Fullerenes are a form of carbon containingfrom 32 atoms to about 960 atoms, which are believed to have thestructure of a spherical geodesic dome, many of which are believed tooccur naturally. The inventors mix a matrix material with fullerenes,and cure the mixture to fabricate a nanoporous dielectric, wherein thefullerenes may be removed from the cured matrix. Although the poresobtained in this manner are generally very uniform in size, homogeneousdistribution of the void carriers still remains problematic. Moreover,both Rostoker's and Kamezaki's methods require addition or admixture ofthe void carriers to a polymeric material, thereby adding essentialprocessing steps and cost in the fabrication of nanoporous materials.

Although various methods are known in the art to introduce nanosizedvoids into low dielectric constant material, all, or almost all of themhave disadvantages. Thus, there is still a need to provide improvedcompositions and methods to introduce nanosized voids in dielectricmaterial.

SUMMARY OF THE INVENTION

The present invention is directed to a method of producing a lowdielectric constant polymer. In one step, a star-shaped thermosettingmonomer having a core structure and a plurality of arms is provided, andin a subsequent step the thermosetting monomer is incorporated into apolymer, wherein the incorporation into the polymer comprises a reactionof a triple bond that is located in at least one arm.

In one aspect of the inventive subject matter, the core structure is acage compound or aryl, and preferred arms are aryl, branched aryl orarylene ether. It is also preferred that where the core structure is acage compound, at least one of the arms has a triple bond. Where thecore structure is an aryl compound, it is preferred that all of the armshave a triple bond. Especially contemplated core structures includeadamantane, diamantane, a phenyl, and a sexiphenylene, and especiallycontemplated arms include a tolanyl, a phenylethynylphenylethynylphenyl,a p-tolanylphenyl, a 1,2-bis(phenylethynyl)phenyl, and a p-tolanylphenylether.

In another aspect of the inventive subject matter, the incorporation ofthe thermosetting monomer includes a reaction on more than one triplebond, preferably on three triple bonds located on three arms, and morepreferably on all triple bonds located in all arms. In particularlypreferred aspects of the inventive subject matter, the incorporationtakes place without participation of an additional molecule andpreferably comprises a cyclo-addition reaction.

While it is generally contemplated that the thermosetting monomer isincorporated in a backbone of a polymer, other positions including thetermini and side chains are also appropriate. Preferred polymers includepoly(arylene ethers) and polymers comprising, or consisting ofcontemplated thermosetting monomers. It is especially contemplated thatby increasing the length of the arms of the thermosetting monomers, themonomers will define an increased void volume between the monomers aftercrosslinking, thereby decreasing the density of the crosslinkedstructure and decreasing the dielectric constant of the polymer.

Various objects, features, aspects and advantages of the presentinvention will become more apparent from the following detaileddescription of preferred embodiments of the invention, along with theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIGS. 1A-1C are exemplary structures for star shaped thermosettingmonomers having an adamantane, a diamantane, and a silicon atom as acage compound, respectively.

FIGS. 2A-2B are exemplary structures for star shaped thermosettingmonomers having a sexiphenylene as an aryl group.

FIGS. 3A-3C are exemplary synthetic schemes for star shapedthermosetting monomers according to the inventive subject matter.

FIG. 4 is an exemplary scheme for the synthesis of substitutedadamantanes with aryl arms of varying length.

DETAILED DESCRIPTION

As used herein, the term “low dielectric constant polymer” refers to anorganic, organometallic, or inorganic polymer with a dielectric constantof approximately 3.0, or lower. As also used herein, the term “cagecompound” refers to a molecule in which a plurality of rings formed bycovalently bound atoms define a volume, such that a point located withinthe volume can not leave the volume without passing through a ring. Forexample, adamantane-type structures, including adamantane and diamantaneare considered a cage compound. In contrast, ring compounds with asingle bridge such as norbornane (bicyclo[2.2.1]heptane) are notconsidered a cage compound, because the rings in a single bridged ringcompound do not define a volume.

In a method of producing a low dielectric constant polymer, athermosetting monomer is provided having a general structure as shown inStructure 1,

wherein Y is selected from a cage compound and a silicon atom, and R₁,R₂, R₃, and R₄ are independently selected from an aryl, a branched aryl,and an arylene ether, and wherein at least one of the aryl, the branchedaryl, and the arylene ether has a triple bond. In a further step, thethermosetting monomer is incorporated into a polymer thereby forming thelow dielectric constant polymer, wherein the incorporation into thepolymer comprises a chemical reaction of the at least one triple bond.As used herein, the term “aryl” without further specification means arylof any type, which may include, for example a branched aryl, or anarylene ether. Exemplary structures of thermosetting monomers thatinclude an adamantane, a diamantane, and a silicon atom are shown inFIGS. 1A, 1B, and 1C, respectively, wherein n is an integer between zeroand five, or more.

In another method of producing a low dielectric constant polymer, athermosetting monomer is provided having a general structure as shown inStructure 2,

wherein Ar is an aryl and R′₁-R′₆ are independently selected from anaryl, a branched aryl, an arylene ether and nothing, and wherein each ofthe aryl the branched aryl, and the arylene ether have at least onetriple bond. In a subsequent step, the thermosetting monomer isincorporated into a polymer thereby forming a low dielectric constantpolymer, wherein the incorporation into the polymer comprises a chemicalreaction of the at least one triple bond. Exemplary structures ofthermosetting monomers that include a tetra-, and a hexasubstitutedsexiphenylene are shown in FIGS. 2A and 2B, respectively.

Thermosetting monomers as generally shown in Structures 1 and 2 may beprovided by various synthetic routes, and exemplary synthetic strategiesfor Structures 1 and 2 are shown in FIGS. 3A-3C. FIG. 3A depicts apreferred synthetic route for the generation of star shapedthermosetting monomers with an adamantane as a cage compound, in which abromoarene is phenylethynylated in a palladium catalyzed Heck reaction.First, adamantane (1) is brominated to tetrabromoadamantane (TBA) (2)following a procedure previously described (J. Org. Chem. 45, 5405-5408(1980) by Sollot, G. P. and Gilbert, E. E.). TBA is reacted with phenylbromide to yield tetrabromophenyladamantane (TBPA) (4) as described inMacromolecules, 27, 7015-7022 (1990) by Reichert, V. R. and Mathias L.J., and TBPA is subsequently reacted with a substituted ethynylaryl in apalladium catalyzed Heck reaction following standard reaction proceduresto yield tetraaylethynylphenyladamantane (TAEPA) (5). Thepalladium-catalyzed Heck reaction may also be employed for the synthesisof a star shaped thermosetting monomer with a sexiphenylene as thearomatic portion, in which a tetrabromosexiphenylene and ahexabromosexiphenylene, respectively, is reacted with an ethynylaryl toyield the desired corresponding star shaped thermosetting monomer.

Alternatively, TBA (supra) can be converted to a hydroxyarylatedadamantane, which is subsequently transformed into a star shapedthermosetting monomer in a nucleophilic aromatic substitution reaction.In FIG. 3B, TBA (2) is generated from adamantane (1) as previouslydescribed, and further reacted in an electrophilic tetrasubstitutionwith phenol to yield tetrakis(hydroxyphenyl)adamantane (THPA) (7).Alternatively, TBA can also be reacted with anisole to givetetrais(4-methoxyphenyl)adamantane (TMPA) (6), which can further bereacted with BBr₃ to yield THPA (7). THPA can then be reacted in variousnucleophilic aromatic substitution reactions with activatedfluoroaromatics in the presence of potassium carbonate employingstandard procedures (e.g., Engineering Plastics—A Handbook ofPolyarylethers by R. J. Cotter, Gordon and Breach Publisheers, ISBN2-88449-112-0 to produce the desired thermosetting monomers, or THPA maybe reacted with 4-halo4′-fluorotolane (with halo=Br or I) in a standardaromatic substitution reaction (e.g., Engineering Plastics, supra) toyield tetrakis[4-(4-halophenylethynylphenoxy)phenyl]adamantane (8). Infurther alternative reactions, various alternative reactants may also beemployed to generate the shaped thermosetting monomers. Similarly, thenucleophilic aromatic substitution reaction may also be utilized in asynthesis of a star shaped thermosetting monomer with a sexiphenylene asthe aromatic portion, in which sexiphenylene is reacted with4-fluorotolane to produce a star shaped thermosetting monomer.Alternatively, phloroglucinol may be reacted in a standard aromaticsubstitution reaction with1-(4-fluorophenylethynyl-4-phenylethynyl)4-benzene to yield1,3,5-tris(phenylethynylphenylethynylphenoxy)benzene.

Where the cage compound is a silicon atom, an exemplary preferredsynthetic scheme is depicted in FIG. 3C, in whichbromo(phenylethynyl)aromatic arms (9) are converted into thecorresponding lithium(phenylethynyl)aromatic arms (10), which aresubsequently reacted with silicon tetrachloride to yield the desiredstar shaped thermosetting monomer with a silicon atom as a cagecompound.

Although it is preferred that the cage compound is an adamantane ordiamantane, in altemative aspects of the inventive subject matter,various cage compounds other than an adamantane or diamantane are alsocontemplated. It should be especially appreciated that the molecularsize and configuration of the cage compound in combination with theoverall length of the arms R₁-R₄ or R′₁-R′₆ will determine the size ofvoids in the final low dielectric constant polymer (by steric effect).Therefore, where relatively small cage compounds are desirable,substituted and derivatized adamantanes, diamantanes, and relativelysmall, bridged cyclic aliphatic and aromatic compounds (with typicallyless than 15 atoms) are contemplated. In contrast, in cases where largercage compounds are desirable, larger bridged cyclic aliphatic andaromatic compounds (with typically more than 15 atoms) and fullerenesare contemplated.

It should further be appreciated that contemplated cage compounds neednot necessarily be limited to carbon atoms, but may also includeheteroatoms such as N, S, O, P, etc. Heteroatoms may advantageouslyintroduce non-tetragonal bond angle configurations, which may in turnenable covalent attachment of arms R₁-R₄ or R′₁-R′₆ at additional bondangles. With respect to substitutes and derivatizations of contemplatedcage compounds, it should be recognized that many substituents andderivatizations are appropriate. For example, where the cage compoundsare relatively hydrophobic, hydrophilic substituents may be introducedto increase solubility in hydrophilic solvents, or vice versa.Alternatively, in cases where polarity is desired, polar side groups maybe added to the cage compound. It is further contemplated thatappropriate substituents may also include thermolabile groups,nucleophilic and electrophilic groups. It should also be appreciatedthat functional groups may be employed in the cage compound (e.g., tofacilitate crosslinking reactions, derivatization reactions, etc.) Wherethe cage compounds are derivatized, it is especially contemplated thatderivatizations include halogenation of the cage compound, and aparticularly preferred halogen is fluorine.

In further alternative aspects of the inventive subject matter, the cagecompound may be replaced by a non-carbon atom with a polygonal, morepreferably tetragonal configuration. Contemplated atoms include asilicon atom, and particularly contemplated atoms include atoms thatexhibit polygonal ligand configuration and form covalent bonds with aresistance to oxidation greater than a carbon-carbon bond. Furthermore,alternative atoms may also include cationic and anionic species of aparticular atom. For example, appropriate atoms are Ge, and P.

Where the thermosetting monomer has an aryl coupled to the arms R′₁-R′₆as shown in Structure 2, it is preferred that the aryl comprises aphenyl group, and it is even more preferred that the aryl is a phenylgroup or a sexiphenylene. In alternative aspects of the inventivesubject matter, it is contemplated that various aryl compounds otherthan a phenyl group or a sexiphenylene are also appropriate, includingsubstituted and unsubstituted bi- and polycyclic aromatic compounds.Substituted and unsubstituted bi- and polycyclic aromatic compounds areparticularly advantageous, where increased size of the thermosettingmonomer is preferred. For example, where it is desirable thatalternative aryls extend in one dimension more than in anotherdimension, naphthalene, phenanthrene, and anthracene are particularlycontemplated. In other cases, where it is desirable that alternativearyls extend symmetrically, polycyclic aryls such as a coronene arecontemplated. In especially preferred aspects, contemplated bi- andpolycyclic aryls have conjugated aromatic systems that may or may notinclude heteroatoms. With respect to substitutions and derivatizationsof contemplated aryls, the same considerations apply as for cagecompounds (vide supra).

With respect to the arms R₁-R₄ and R′₁-R′₆, it is preferred that R₁-R₄are individually selected from an aryl, a branched aryl, and an aryleneether, and R′₁-R′₆are individually selected from an aryl, a branchedaryl, and an arylene ether, and nothing. Particularly contemplated arylsfor R₁-R₄ and R′₁-R′₆ include aryls having a tolanyl, aphenylethynylphenylethynylphenyl, and a p-tolanylphenyl moiety, andtolanyl, phenylethynylphenylethynylphenyl, and p-tolanylphenyl moieties.Especially preferred branched aryls include a1,2-bis(phenylethynyl)phenyl, and particularly contemplated aryleneethers include p-tolanylphenyl ether.

In alternative aspects of the inventive subject matter, appropriate armsneed not be limited to an aryl, a branched aryl, and an arylene ether,so long as alternative arms R₁-R₄ and R′₁-R′₆comprise a reactive group,and so long as the incorporation of the thermosetting monomer comprisesa reaction involving the reactive group. The term “reactive group” asused herein refers to any element or combinations of elements havingsufficient reactivity to be used in incorporating the monomer into apolymer. For example, contemplated arms may be relatively short with nomore than six atoms, which may or may not be carbon atoms. Such shortarms may be especially advantageous where the size of voids incorporatedinto the final low dielectric constant polymer need to be relativelysmall. In contrast, where especially long arms are preferred, the armsmay comprise a oligomer or polymer with 7-40, and more atoms.Furthermore, the length as well as the chemical composition of the armscovalently coupled to the contemplated thermosetting monomers may varywithin one monomer. For example, a cage compound may have two relativelyshort arms and two relatively long arms to promote dimensional growth ina particular direction during polymerization. In another example, a cagecompound may have two arms chemically distinct from another two arms topromote regioselective derivatization reactions.

It should further be appreciated that while it is preferred that all ofthe arms in a thermosetting monomer have at least one reactive group, inalternative aspects less than all of the arms need to have a reactivegroup. For example, a cage compound may have 4 arms, and only 3 or twoof the arms carry a reactive group. Alternatively, an aryl in athermosetting monomer may have three arms wherein only two or one armhas a reactive group. It is generally contemplated that the number ofreactive groups in each of the arms R₁-R₄ and R′₁-R′₆ may varyconsiderably, depending on the chemical nature of the arms and of thequalities of the desired end product. Moreover, reactive groups arecontemplated to be positioned in any part of the arm, including thebackbone, side chain or terminus of an arm. It should be especiallyappreciated that the number of reactive groups in the thermosettingmonomer may be employed as a tool to control the degree of crosslinking.For example, where a relatively low degree of crosslinking is desired,contemplated thermosetting monomers may have only one or two reactivegroups, which may or may not be located in one arm. On the other hand,where a relatively high degree of crosslinking is required, three ormore reactive groups may be included into the monomer. Preferredreactive groups include electrophilic and nucleophilic groups, morepreferably groups that may participate in a cyclo addition reaction anda particularly preferred reactive group is an ethynyl group.

In addition to reactive groups in the arms, other groups, includingfunctional groups may also be included into the arms. For example, whereaddition of particular functionalities (e.g., a thermolabile portion)after the incorporation of the thermosetting monomer into a polymer isdesirable, such functionalities may be covalently bound to thefunctional groups.

The thermosetting monomers can be incorporated into a polymer by a largevariety of mechanisms, and the actual mechanism of incorporationpredominantly depends on the reactive group that participates in theincorporation. Therefore, contemplated mechanisms include nucleophilic,electrophilic and aromatic substitutions, additions, eliminations,radical polymerizations, and cycloadditions, and a particularlypreferred incorporation is a cycloaddition that involves at least oneethynyl group located at least one of the arms. For example, in athermosetting monomer having arms selected from an aryl, a branched aryland an arylene ether, in which at least three of the aryl, the branchedaryl, and the arylene ether have a single triple bond, the incorporationof the monomer into the polymer may comprise a cycloaddition reaction(i.e. a chemical reaction) of at least three triple bonds. In anotherexample, in a thermosetting monomer wherein all of the aryl, thebranched aryl, and the arylene ether arms have a single triple bond, theincorporation of the monomer into the polymer may comprise acycloaddition (i.e. a chemical reaction) of all of the triple bonds. Inother examples, cycloadditions (e.g., a Diels-Alder reaction) may occurbetween an ethynyl group in at least one arm of the thermosettingmonomer and a diene group located in a polymer. It is furthercontemplated that the incorporation of the thermosetting monomers into apolymer takes place without participation of an additional molecule(e.g., a crosslinker), preferably as a cyclo addition reaction betweenreactive groups of thermosetting monomers. However, in alternativeaspects of the inventive subject matter, crosslinkers may be employed tocovalently couple a thermosetting monomer to a polymer. Such covalentcoupling may thereby either occur between a reactive group and a polymeror a functional group and a polymer.

Depending on the mechanism of incorporation of the thermosetting monomerinto the polymer, reaction conditions may vary considerably. Forexample, where a monomer is incorporated by a cycloaddition employing atriple bond of at least one of the arm, heating of the thermosettingmonomer to approximately 250° C. for about 45 min is generallysufficient. In contrast, where the monomer is incorporated into apolymer by a radical reaction, room temperature and addition of aradical starter may be appropriate. A preferred incorporation is setforth in the examples.

With respect to the position of incorporation of the thermosettingmonomer into polymer it is contemplated that thermosetting monomers maybe incorporated into the backbone, a terminus or a side chain of thepolymer. As used herein, the term “backbone” refers to a contiguouschain of atoms or moieties forming a polymeric strand that arecovalently bound such that removal of any of the atoms or moiety wouldresult in interruption of the chain.

Contemplated polymers include a large variety of polymer types such aspolyimides, polystyrenes, polyamides, etc. However, it is especiallycontemplated that the polymer comprises a polyaryl, more preferably apoly(arylene ether). In an even more preferred aspect, the polymer isfabricated at least in part from the thermosetting monomer, and it isparticularly contemplated that the polymer is entirely fabricated fromthe thermosetting monomer.

It should be especially appreciated that (1) the size of the cagecompound or the aryl, and (2) the overall length of the arms R₁-R₄ andR′₁-R′₆ that are covalently coupled to the cage compound will determinethe nanoporosity imparted by a steric effect. Therefore, where athermosetting monomer with a cage compound or a silicon atom is part ofa low dielectric constant polymer, and wherein the arms R₁-R₄ have atotal length L and the low dielectric constant polymer has a dielectricconstant K, the dielectric constant K will decrease when L increases.Likewise, where a thermosetting monomer with an aryl is part of a lowdielectric constant polymer, and wherein the arms R′₁-R′₆ have a totallength L and the low dielectric constant polymer has a dielectricconstant K, the dielectric constant K will decrease when L increases.Consequently, the size of the cage compound, the aryl, and particularlythe size of the arms in a thermosetting monomer can be employed to finetune or regulate the dielectric constant of a low dielectric constantpolymer harboring the thermosetting monomer. It is especiallycontemplated that by extension of the arms in a thermosetting monomerthe dielectric constant may be reduced in an amount of up to 0.2,preferably of up to 0.3, more preferably of up to 0.4 and mostpreferably of up to 0.5 dielectric constant units.

In an especially contemplated arm extension strategy depicted in FIG. 4,in which AD represents an admantane or diamantane group. Phenylacetyleneis a starting molecule that is reacted (A1) with TBA (supra) to yieldtetrakis(mono-tolanyl)-adamantane. Alternatively, phenylacetylene can beconverted (B1) to tolanylbromide that is subsequently reacted (C1) withtrimethylsilylacetylene to form tolanylacetylene. TBA can then bereacted (A2) with tolanylacetylene to tetrakis(bistolanyl)-adamantane.In a further extension reaction, tolanylacetylene is reacted (B2) with1-bromo-4-iodobenzene to bistolanylbromide that is further converted(C2) to bistolanylacetylene. The so formed bistolanylacetylene may thenbe reacted (A3) with TBA to yield tetrakis(tristolanyl)-adamantane.

It is particularly contemplated that the thermosetting monomersaccording to the inventive subject matter may be employed in adielectric layer of an electronic device, wherein preferred dielectriclayers have a dielectric constant of less than 3, and preferred electricdevices include an integrated circuit. Therefore, a contemplatedelectrical device may include a dielectric layer, wherein the dielectriclayer comprises a polymer fabricated from a thermosetting monomer havingthe structures

wherein Y is selected from a cage compound and a silicon atom, Ar ispreferably an aryl, R₁-R₄ are independently selected from an aryl, abranched aryl, and an arylene ether, R′₁-R′₆ are independently selectedfrom an aryl, a branched aryl, and an arylene ether and nothing, andwherein at least one of the aryl, the branched aryl, and the aryleneether has a triple bond.

EXAMPLES

The following examples describe exemplary syntheses of thermosettingmolecules according to the inventive subject matter, and preparation ofa low dielectric constant film.

Example 1

Adamantane is brominated to TBA following a procedure as previouslydescribed in J. Org. Chem. 45, 5405-5408 (1980), by Sollot, G. P. andGilbert, E. E.

TBA was reacted with bromobenzene to yieldtetrakis(3/4-bromophenyl)adamantane (TBPA) as described inMacromolecules, 27, 7015-7022 (1990) by Reichert, V. R. and Mathias L.J. The reaction resulted in the formation of various byproducts. HPLC-MSanalysis showed that the yield of the desired TBPA was approximately50%, accompanied by 40% of the tribrominated tetraphenyl adamantane andabout 10 % of the dibrominated tetraphenyladamantane. Unexpectedly,however, when the product mixture was subjected to fresh reagent andcatalyst (bromobenzene and AlCl₃, 1 min at 20° C.), TBPA was obtained inyields of approximately 90%.

TBPA was reacted with phenylacetylene to yield the final producttetrakis(tolanyl)adamantane following a general reaction protocol for apalladium-catalyzed Heck ethynylation.

Example 2

In a 500-mL 3-neck round-bottom flask, equipped with an addition funneland a nitrogen gas inlet, 4-iodobromobenzene (25.01 g, 88.37 mmoL),triethylamine (300 mL), bis(triphenylphosphine)-paladium[II] chloride(0.82 g) and copper[I] iodide (0.54 g) were added. Then, a solution ofphenylacetylene (9.025 g, 88.37 mmoL) in triethylamine (50 mL) was addedslowly, and the temperature of the solution was kept under 35 C understirring. The mixture was stirred for another 4 hours after addition wascompleted. The solvent was evaporated on the rotary evaporator and theresidue was added to 200 mL of water. The product was extracted withdichloromethane (2×150 mL). The organic layers were combined and thesolvents were removed by rotary evaporator. The residue was washed with80 mL hexanes and filtered TLC and HPLC showed a pure product (yield,19.5 g, 86%). Additional purification was performed by short silicacolumn chromatography (Eluent is 1:2 mixture of toluene and hexanes). Awhite crystalline solid was obtained after solvent removal. The purityof the product was characterized by GC/MS in acetone solution, andfurther characterized by proton NMR.

The synthesis of p-ethynyltolane from p-bromotolane was performed in twosteps. In the first step, p-bromotolane was trimethylsilylethynylated,and in the second step, the reaction product of the first step wasconverted to the final endproduct

-   Step 1 (Trimethylsilylethynylation of 4-bromotolane): 4-Bromotolane    (10.285 g, 40.0 mMol), ethynyltrimethylsilane (5.894 g, 60.0 mMol),    0.505 g (0.73 mMol) of dichlorobis(triphenylphosphine)-palladium[II]    catalyst, 40 mL of anhydrous triethylamine, 0.214 g (1.12 mMol) of    copper[I] iodide, and 0.378 g (1.44 mMol) of triphenylphosphine were    placed into the N₂ purged, 5-Liter 4-neck round-bottom flask,    equipped with an overhead mechanical stirrer, condenser, and    positioned inside a heating mantle. The mixture was heated to a    gentle reflux (about 88° C.) and maintained at reflux for 1.5 hours.    The reaction mixture became a thick black paste and was cooled.    Thin-layer chromatographic analysis indicated complete conversion of    starting material 4-bromtolane to a single product. The solids were    filtered and washed with 50 mL of triethylamine, mixed with 400 mL    of water and stirred for 30 minutes. The solids was filtered and    washed with 40 mL of methanol. The crude solid was recrystallized    from 500 mL of methanol. On standing, lustrous silver colored    crystals settled out. They were isolated by filtration and washed    with 2×50 mL of methanol. 4.662 g was recovered (42.5% yield).-   Step 2 (Conversion of 4-(Trimethylsilyl)ethynyltolane to    4-Ethynyltolane): To a 1 -Liter 3 neck round-bottom flask equipped    with a nitrogen inlet, an overhead mechanical stirrer, was charged    800 mL of anhydrous methanol, 12.68 g (46.2 mMol) of    4-(trimethylsilyl)ethynyltolane, and 1.12 g of anhydrous potassium    carbonate. The mixture was heated to 50° C. Stirring continued until    no starting material is detected by HPLC analysis (about 3 hours).    The reaction mixture was cooled. The crude solids were stirred in 40    mL of dichloromethane for 30 min and filtered. The filtered    suspended solids by HPLC showed mainly impurities. The    dichloromethane filtrate was dried and evaporated to yield 8.75 g of    a solid. On further drying in an oven, the final weight was 8.67 g,    which represented a yield of 92.8%.    TBPA (supra) was reacted with 4-ethynyltolane to yield the final    product tetrakis(bis-tolanyl)adamantane (TBTA) following a general    protocol for a palladium-catalyzed Heck ethynylation reaction.

The so prepared TBTA was dissolved in cyclohexanone to obtain a 10% (byweight) solution, 5ml of which were spun onto two silicon wafers usingstandard procedures well known in the art. The TBTA was polymerized onthe wafer by heating to a temperature of about 300° C., and cured at atemperature of 400° C. for 1 hour. The k-value was determined to be2.57. It should be especially appreciated that when the k-value wascompared to the k-value of TTA, (which is a is a structural analog toTBTA with a shortened length of the arms) the k-value of TTA was higherat about 2.60. Thus, the contemplated decrease in the k-value due to anincreased length of the arms extending from the cage compound has beenexperimentally confirmed.

Thus, specific embodiments and applications of compositions and methodsto produce a low dielectric constant polymer have been disclosed. Itshould be apparent, however, to those skilled in the art that many moremodifications besides those already described are possible withoutdeparting from the inventive concepts herein. The inventive subjectmatter, therefore, is not to be restricted except in the spirit of theappended claims. Moreover, in interpreting both the specification andthe claims, all terms should be interpreted in the broadest possiblemanner consistent with the context. In particular, the terms “comprises”and “comprising” should be interpreted as referring to elements,components, or steps in a non-exclusive manner, indicating that thereferenced elements, components, or steps may be present, or utilized,or combined with other elements, components, or steps that are notexpressly referenced.

1. A method of producing a low dielectric constant polymer, comprising:providing a thermosetting monomer having the structure

wherein Ar is an aryl or a cage compound, and R′₁, R′₂, R′₃, R′₄, R′₅,and R′₆ comprise an aryl, a branched aryl, an arylene ether, and ahydrogen atom, and wherein each of the aryl, the branched aryl, and thearylene ether have at least one triple bond; and incorporating thethermosetting monomer into a polymer thereby forming the low dielectricconstant polymer, wherein the incorporation into the polymer comprises achemical reaction of the at least one triple bond.
 2. The method ofclaim 1 wherein the aryl comprises a phenyl group.
 3. The method ofclaim 2 wherein Ar is selected from the group consisting of a phenylgroup and a sexiphenylene.
 4. The method of claim 1 wherein R′₁, R′₂,R′₃, R′₄, R′₅ and R′₆ have a total length L, and the low dielectricconstant polymer has a dielectric constant K, and wherein K decreaseswhen L increases.
 5. The method of claim 1 wherein the step ofincorporating the thermosetting monomer into the polymer takes placewithout participation of an additional molecule.
 6. The method of claim1 wherein the polymer comprises a poly(arylene ether).
 7. The method ofclaim 1, wherein the cage compound comprises an adamantane molecule or adiamantane molecule.
 8. A thermosetting monomer having the structure

wherein Ar is an aryl or a cage compound, and R′₁, R′₂, R′₃, R′₄, R′₅and R′₆ are independently selected from an aryl, a branched aryl, anarylene ether, and a hydrogen atom, and wherein each of the aryl, thebranched aryl, and the arylene ether have at least one triple bond. 9.The monomer of claim 8, wherein the cage compound comprises anadamantane molecule or a diamantane molecule.
 10. A thermosettingmonomer having a structure according to formula TM-3:


11. An electrical device including a dielectric layer comprising apolymer fabricated from at least one thermosetting monomer comprising:

wherein Y is selected from a cage compound and a silicon atom, and R₁,R₂, R₃, and R₄ re independently selected from an aryl, a branched aryl,and an arylene ether, and wherein at least one of the aryl, the branchedaryl, and the arylene ether has a triple bond;

wherein Ar is an aryl or a cage compound, and R′₁, R′₂, R′₃, R′₄, R′₅,and R′₆ are independently selected from an aryl, a branched aryl, anarylene ether, and a hydrogen atom, and wherein each of the aryl, thebranched aryl, and the arylene ether have at least one triple bond;


12. The electrical device of claim 11, wherein the cage compoundcomprises an adamantane molecule or a diamantane molecule.